Measuring spike train synchrony

Estimating the degree of synchrony or reliability between two or more spike trains is a frequent task in both experimental and computational
neuroscience. In recent years, many different methods have been proposed that typically compare the timing of spikes on a certain time scale to
be optimized by the analyst. Here, we propose the ISI-distance, a simple complementary approach that extracts information from the interspike
intervals by evaluating the ratio of the instantaneous firing rates. The method is parameter free, time scale independent and easy to visualize as
illustrated by an application to real neuronal spike trains obtained in vitro from rat slices. In a comparison with existing approaches on spike trains
extracted from a simulated Hindemarsh-Rose network, the ISI-distance performs as well as the best time-scale-optimized measure based on spike
timing.